Bulk metallic glasses (“BMG”) have generated interest as structural materials due to their unique mechanical properties, which include high strength and large elastic elongation. Metallic glasses, unlike conventional crystalline alloys, have an amorphous or disordered atomic-scale structure that gives them unique properties. For instance, metallic glasses have a glass transition temperature (Tg) above which they soften and flow. This characteristic allows for considerable processing flexibility. Known metallic glasses have only been produced in thin ribbons, sheets, wires, or powders due to the need for rapid cooling from the liquid state to avoid crystallization. A recent development of bulk glass-forming alloys, however, has obviated, this requirement, allowing for the production of metallic glass ingots greater than one centimeter in thickness. This development has permitted the use of metallic glasses in engineering applications where their unique mechanical properties, including high strength and large elastic elongation, are advantageous.
A common limitation of conventional metallic glasses, however, is their tendency to experience plastic deformation in narrow regions called shear bands. This localized deformation increases the likelihood that metallic glasses will fail in an apparently brittle manner in any loading condition (such as tension) where the shear bands are unconstrained. As a result, monolithic metallic glasses typically display limited plastic flow (0-4% under uniaxial compression) at ambient or room temperature. This lack of widespread plastic deformation results in low toughness. Toughness is a critical parameter in any structural material.